Note: Descriptions are shown in the official language in which they were submitted.
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Method for producing a dentist tool
The present invention concerns a method for producing a
dentist tool formed by an overlay to be used by a dentist in removing
tooth structure from a tooth, said method comprising the steps of:
determining a predetermined part of tooth structure to be removed
so as to prepare said tooth for further treatment;
determining an overlay fitting said tooth and fitting at least a part
of a neighbouring tooth of said tooth;
simulating a movement to be followed by a dentist cutting tool in
order to remove at least a part of said predetermined part;
determining a first guiding edge within said overlay, said first
guiding edge corresponding to said movement so that it is provided to
contact said dentist cutting tool following said movement, thereby being
provided to guide said dentist cutting tool in a predetermined position,
is said first guiding edge being part of a guiding means;
producing said determined overlay with said guiding means.
The present invention further concerns a dentist tool to be
used by a dentist in removing tooth structure from a tooth of a patient,
which tooth is to be prepared for further treatment, said dentist tool
comprising:
an overlay having a shape and dimensions so that it is releasably
fixable over said tooth and being attachable to that tooth or to at least a
part of a neighbouring tooth of said tooth;
a first guiding edge within said overlay that is provided to contact
a dentist cutting tool following a predetermined movement, said first
guiding edge thereby being provided to guide said dentist cutting in a
predetermined position.
When a patient needs a crown, bridge, onlay, inlay, veneer,
or other restoring or other dental prosthesis and/or aesthetic tooth
treatment, conventionally, during an initial office visit, the dentist
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identifies the needs of the patient and determines an appropriate
treatment. During subsequent visits, in case the tooth comprises
damaged and/or infected tooth structure, the dentist removes this tooth
structure and reconstructs the tooth as much as possible using
conventional techniques. Thereafter, the dentist performs the final
preparation of the tooth for further treatment by removing tooth material,
which is to be interpreted as original tooth structure and reconstructed
tooth structure, with a dental cutting tool such as a high-speed drill.
Relying upon eyesight and expertise, the dentist uses the drill to shape
the tooth in a form that is suitable for further treatment, in particular a
form onto which a crown, bridge, onlay, inlay, veneer or other tooth
restoring part can be mounted. Then, the dentist takes an impression of
the dental arch in which the prepared tooth is located, and sends the
impression to the dental laboratory to have the dental technician make
the restoration part. Using the impression of the prepared tooth, the
dental technician produces a restoration part that matches the colour,
geometrical and material specifications, and sends it to the dentist. At
the patient's final visit, the dentist adjusts the restoration part as
necessary before fitting it in place.
A further dentist tool is disclosed in EP1547544. This
dentist tool decreases the impact of the experience and expertise of the
dentist onto the treatment, and it is used by a dentist in boring an
artificial tooth root cavity. In EP1547544, guiding means, formed by a
cylindrical hole, for guiding a drill in a straight-forward way, is provided.
In such a manner an artificial tooth root cavity can be bored with greater
precision even by a less experienced dentist. Moreover a suitable root
cavity position can be calculated based on the information processed by
the computer, so as to form in the most optimal way a cavity in the jaw
bone.
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A drawback of the known dentist tool is that it can only be
used by a dentist in boring holes into the jaw bone. This dentist tool is
not suitable to be used by a dentist in preparing a tooth for further
treatment.
A further dentist tool is disclosed in DE4012327, which is
considered close prior art. This dentist tool is formed by a template that
comprises a guiding edge for guiding a dentist cutting tool along a
predetermined movement. The guiding edge is provided at a
predetermined height so that besides the position, also the depth of the
dentist cutting tool can be guided. DE4012327 furthermore teaches how
the dentist can use the template by placing the template in the mouth of
the person and, using a moving-plate fixing the tilt of the dentist cutting
tool into a predetermined inclination, running with the dentist cutting tool
along the guiding edge thereby removing predetermined tooth structure.
is A drawback of this known dentist tool is that the tilt is,
because of the moving-plate, fixed in a predetermined inclination.
Thereby, the dentist tool can not guide a dentist cutting tool in a complex
movement where also tilt variations occur. In particular when working
with complex surfaces such as teeth, such complex movements are
preferable.
It is an object of the present invention to provide method for
producing a dentist tool that is suitable for guiding a dentist cutting tool
along a complex movement.
To this end, the method for producing a dentist tool
according to the present invention is characterized in that said method
comprises the further steps of:
determining a second guiding edge within said overlay that is
spaced apart from said first guiding edge by a distance d of at least 0.5
mm, said second guiding edge corresponding to said movement so that it
is provided to simultaneously with said first guiding edge contact said
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dentist cutting tool following said movement, said first and second
guiding edge thereby being provided to guide said dentist cutting tool in
a predetermined tilt, said second guiding edge being part of said guiding
means.
The presence of the second guiding edge in the overlay
results therein that the movement of a dentist cutting tool can be guided
along a predetermined surface, whereas, in the prior art, the movement
of the tool can only be guided along a predetermined line. Thereby also
a guidance of the inclination of the dentist cutting tool can be obtained,
which is not possible in the prior art. The presence of the second guiding
edge results in that a dentist cutting tool can be guided along complex
movements where position variations as well as tilt variations occur.
The determination of a predetermined part of tooth structure
to be removed has the effect that this does not any more depend on the
skills of the dentist. Determining and producing guiding edges into an
overlay, which guiding edges are suitable for simultaneously contacting
the dentist cutting tool, allows the cutting tool to be guided along a well
determined path in an at least partially predetermined way. The overlay,
having the guiding edges, accurately indicates onto the tooth the part to
be removed from the tooth as determined by the computer. Moreover the
tool according to the invention is provided to assist the dentist in
removing tooth structure as the tool allows a dentist to remove at least
part of a predetermined part of tooth structure.
It is to be noted that the term fitting is not to be interpreted
in the narrow sense that the overlay should closely surround the teeth. It
moreover should be interpreted as that an overlay should surround the
teeth so as to be adequately in contact with the teeth and so that, once
applied, it will not be released even if certain pressure, due to a normal
use of the overlay, is applied.
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Preferably, the method of this invention further comprises
the steps of:
acquiring three-dimensional data relating to a shape of at least
said tooth and at least said part of said neighbouring tooth;
s processing said three-dimensional data with a computer so as to
determine significant dimensions and orientations for said overlay;
processing said three-dimensional data to determine said
predetermined part.
Depending on the individual dental situation of a patient,
io the computer is programmed to determine an optimal way for shaping the
tooth into a shape that is suitable for further treatment.
In a preferred embodiment of the invention, said first and
said second guiding edge are designed for simultaneously contacting
said dentist cutting tool at contacting points being longitudinally
15 distanced from each other by said distance, said guiding edges thereby
defining a guiding surface along which said dentist cutting tool is to be
guided.
By simultaneously contacting two guiding edges with a
cutting tool at contacting points being longitudinally distanced from each
20 other, the cutting tool can be guided at least partially in a predetermined
way. Preferably the cutting tool moves along the two guiding edges and
thereby defines a guiding surface. This surface comprises the two
guiding edges, and a cutting tool can be guided along this surface. This
allows an accurate guiding in two dimensions.
25 Preferably, said guiding means comprise a guiding groove,
which defines a path extending in a surface of said overlay and suitable
for guiding said dentist cutting tool along said path in such a manner as
to enable a guided removal of at least partially said predetermined part
of tooth structure.
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The two guiding edges, being distanced from each other,
can be located one on the one side and the other on the other side of the
path thereby defining the path between the two guiding edges. To this
purpose, the distance between the two guiding edges should be
substantially equal to a diameter of the cutting tool. Using the dentist
cutting tool by simultaneously contacting the two guiding edges and
following the path allows a guidance of the cutting tool at least in two
dimensions. Considering a longitudinal cutting tool, the surface defined
by the two guiding edges in this configuration will be substantially
perpendicular to the direction of the cutting tool in use. The preferred tilt
of the cutting tool, in this configuration, is perpendicular to the plane that
is formed by the two guiding edges.
The two guiding edges, being distanced from each other,
can also be both located on one side of the path. At least a third guiding
edge will then define the other side of the path. Considering a
longitudinal cutting tool in this configuration, the surface defined by the
two guiding edges will be substantially parallel to the direction of the
cutting tool in use. The third guiding edge in this configuration will
provide a further guidance to the cutting tool thereby increasing the
accuracy of the process of removal of tooth structure. Using the dentist
tool by simultaneously contacting the two guiding edges and following
the path in this configuration allows a guidance of the cutting tool in two
dimensions and a guidance of inclination of the cutting tool.
Preferably, the method comprises the further steps of:
producing a tooth restoration part having an inner shape
determined so as to fit a predetermined remaining part of tooth structure
of said tooth, and having an outer shape determined so as to fit together
with remaining neighbouring teeth.
An advantage of the method according to the invention is
that the shape of the remaining part of tooth structure of the prepared
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tooth is known in advance due to the guided removal of tooth structure.
This improves further treatment, such as preparing a temporary or final
inlay, onlay, bridge, crown or veneer in advance based on the three-
dimensional data. This results in that less office visits are required, as
the dentist can both prepare the tooth and mount the tooth restoration
part onto the prepared tooth in one single visit. This way of working does
not only save time and thus costs, also the inconvenience for the patient
is strongly decreased. Furthermore the chances that a prepared tooth
gets contaminated, and the resulting complications, are reduced to a
minimum.
Preferably, the method comprises the further steps of:
processing said three-dimensional data to simulate a tooth
restoration part having an inner shape determined so as to fit a
predetermined remaining part of tooth structure of said tooth, and having
an outer shape determined so as to fit together with remaining
neighbouring teeth;
producing said tooth restoration part.
Thereby, an individually designed tooth restoration part can
be delivered together with the dentist tool according to the invention.
This is possible because the final shape of the prepared tooth, when
using the dentist tool, is known in advance. The result is that less dental
visits are required to place a restoration part.
Preferably, said predetermined part is determined by:
firstly determining an outer shape of said tooth restoration part so
that it fits together with remaining neighbouring teeth, and determining
an inner shape of said tooth restoration part that is compatible with said
outer shape;
secondly determining a shape of remaining tooth structure so that
said tooth restoration part having said inner shape fits said shape of
remaining tooth structure;
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thirdly determining said predetermined part as being the part of
tooth structure to be removed so as to have said shape of remaining
tooth structure left.
Starting with determining a tooth restoration part instead of,
as conventionally, preparing the tooth, has an advantage. A tooth
restoration part can be determined having an outer shape so as to
optimally fit together with remaining neighbouring teeth. Procedures for
determination of such an outer shape are known to the person skilled in
the art. An inner shape is then determined, which inner shape is
compatible with said outer shape. Criteria for being compatible depend
on the material that is to be used and mainly concern strength
parameters, production parameters and parameters relating to the
mounting of the restoration part onto the tooth and/or teeth. Preferably
the inner shape is determined in such a manner that a minimum amount
of material is required to produce the tooth restoration part. This at its
turn results in that the remaining tooth structure, required to fit to this
inner shape, is as large as possible, namely, the more material of a
restored tooth is tooth restoration material, the less material of that
restored tooth is tooth structure. Then the predetermined part can be
determined as being the part of tooth structure to be removed so as to
have said shape of remaining tooth structure left. Thus first determining
the tooth restoration part, results in that a minimum of tooth structure is
to be removed from the tooth and maximum conservation of the original
tooth structure. As it is best to maintain as much of the original tooth
structure, this is an advantage.
Providing the determined tooth restoration part having the
determined outer and inner shape together with the dental tool, results in
that less office visits are required because the dentist can prepare the
tooth and mount the tooth restoration part onto the prepared tooth in one
single visit.
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Preferably said dentist tool comprises at least one further
overlay, said overlay and said at least one further overlay being
determined to guide a dentist tool in removing tooth structure in a
plurality of stages, in which said guiding means in said overlay is
provided to guide said cutting tool in one of said plurality of stages, and
at least one further guiding means in said at least one further overlay is
provided to guide said cutting tool in at least one further of said plurality
of stages, the method further comprising the steps of:
determining at least one further overlay fitting said tooth and fitting
at least a part of said neighbouring tooth;
simulating at least one further movement to be followed by said
dentist cutting tool in order to remove at least one further part of said
predetermined part;
determining at least one further first guiding edge within said at
least one further overlay, said at least one further first guiding edge
corresponding to said at least one further movement so that it is provided
to contact said dentist cutting tool following said at least one further
movement, thereby being provided to guide said dentist cutting tool in a
predetermined position, said at least one further first guiding edge being
part of said at least one further guiding means;
determining at least one further second guiding edge within said
at least one further overlay that is spaced apart from said at least one
further first guiding edge by a distance d of at least 0.5 mm, said at least
one further second guiding edge corresponding to said at least one
further movement so that it is provided to simultaneously with said at
least one further first guiding edge contact said dentist cutting tool
following said at least one further movement, said at least one further
first and second guiding edge thereby being provided to guide said
dentist cutting tool in a predetermined tilt, said at least one further
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second guiding edge being part of said at least one further guiding
means
producing said at least one further overlay with said at least one
further guiding means.
Producing a plurality of overlays instead of just one overlay
provides a further flexibility in the method for producing the dentist tool.
Different overlays can be provided for guiding a dentist cutting tool along
different sides of the tooth to be prepared, so that for example a
circumferential path can be defined by using multiple overlays each
defining a different segment of the circumferential path. Multiple overlays
furthermore allow to use different dental cutting tools, which is necessary
in some cases. Different overlays can be provided for preparing a tooth
in multiple stages, in which for example a first stage is provided to
smoothen the upper part of the tooth, a second and a third stage are
provided to cut away the longitudinal and transversal sides of the tooth,
and a fourth and fifth stage are provided to round off the edges between
the longitudinal and transversal sides each at a different side of the
tooth. Preparing a tooth in stages allows each overlay to be designed
having guiding edges which are particularly determined for guiding the
cutting tool in a particular way characterised by the particular stage.
The invention will now be described in more details with
respect to the drawings illustrating some preferred embodiments of the
invention. In the drawings:
figure 1 shows a top view of an overlay with a guiding
groove according to the invention;
figure 2 shows a side view of an overlay with a guiding
groove placed onto a patient's teeth.
figure 3 shows a cross section of part of an overlay with
guiding means according to one embodiment of the invention and a
cutting tool;
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figure 4 shows a cross section of part of an overlay with
guiding means according to another embodiment of the invention and a
cutting tool;
figure 5 shows a cross section of part of an overlay with
guiding means according to the invention and a cutting tool;
figure 6 shows a cross section of part of an overlay with
guiding means according to a further embodiment of the invention and a
cutting tool;
figure 7 shows a set of overlays to be used by a dentist in
io preparing a tooth for mounting a crown or bridge.
figure 8 shows a cross-section of the overlay shown in
figure 7a.
In the drawings a same reference number has been
allocated to a same or analogous element.
The terms "lower", "upper" etc. and derived directional
terms such as "horizontal" and "vertical" are based on a normal
configuration of an overlay as shown in the drawings, wherein the
overlay fits onto teeth with their root extending vertically downward. The
term dentist in this text is not to be interpreted restrictive and can also be
read as dental technician, dental assistant, dental auxiliary, dental
therapist, dental designer etc.
The invention provides a method for producing a dentist
tool formed by an overlay 1 to be used by a dentist in removing tooth
structure. Furthermore, the invention provides an overlay 1 obtainable by
this method. Figure 1 and 2 show such an overlay 1 arranged onto the
teeth 2 of a patient. Preferably, the invention provides a method for
producing the dentist tool and a tooth restoration part in such a manner
that the tooth restoration part will fit the tooth that is prepared using the
dentist tool.
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The dentist tool according to the invention is preferably
used by a dentist in preparing a tooth for a restoration such as placing
inlays and onlays, crowns, bridges, and veneers. Such restoration
requires a restoration part to be produced in order to fit the tooth after
the latter has been prepared. Using the dentist tool according to the
invention results in that the shape of the prepared tooth, which
conventionally is only known after preparation, is determined in advance.
Based on this knowledge, a restoration part can be produced in advance
so that this restoration part is available to the dentist even before he or
io she starts preparing the tooth, and can be mounted directly after
preparation of the tooth. This results in that the patient suffers less
inconvenience, in particular that the number of visits to the dentist are
reduced. Furthermore the chances that a prepared tooth gets
contaminated, and the resulting complications, are reduced to a
minimum.
Preferably, preparing a tooth for further treatment is
performed onto a substantially healthy tooth. When a tooth is damaged
or infected, the damaged and/or infected parts of the tooth will have to be
removed first, and the tooth will have to be reconstructed before
preparing the tooth for further treatment. This minimizes the chance that
an infection develops underneath a tooth restoration part. This also
maximizes the lifetime of the tooth restoration part as the basis for the
tooth restoration part, namely the tooth, does not contain damaged parts
any more.
It may be possible to utilize an overlay made for one tooth
in the preparation of a tooth of another patient, where such other
patient's tooth has sufficiently similar dimensions and shape. Therefore,
it is within the scope of this invention to have prepared some overlays
which can be standardized, reused and/or reproduced. Also, it is within
the scope of this invention to utilize data obtained in the preparation of
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prior overlays and restoration parts in the design and generation of new
overlays having substantially similar dimensions and shapes.
Several methods are known for acquiring three-dimensional
data from a patient's dentition. Such data can be retrieved, for example
by processing photographs taken from the patient's dentition. Another
method is making a physical impression of the dentition and then
subsequently scanning this impression or a reversed cast of the
impression. Such scanning can be conducted with a CAD/CAM 3D
scanning device. Illustrative of such a device is the FreeForm from
SensAble Technologies Inc. of Woburn, Massachusetts, USA. While
such a scanning device can scan a model of the dental arch with a
tolerance of about 10 pm this does not take into account other error
factors obtained from the making of the impression and the casting of the
dental impression. In preparing the ultimate restoration part or dental
prosthesis, these other error factors or tolerances must be considered. .
The CAD program chooses the specific configuration for
the overlay, sometimes referred to as reduction trays, and ultimately the
configuration for the prepared tooth by utilizing certain protocols which
are based on prior experience for preparing dental prostheses.
In one embodiment of the invention, the digital file for the
subject tooth can be compared with an existing database for such
prostheses. Such an illustrative database is available from Heraeus
Kulzer Tooth Library of Heraeus Kulzer GmbH of Hanau Germany. This
data base has also been integrated into the SensAble Dental Lab
System (SDLS). A prothesis (e.g. a crown or onlay) comparable to that
appropriate for the subject tooth is chosen from the Kulzer database.
That prosthesis information includes the configuration and dimensions
for the prepared tooth, which would correspond to the internal surface of
the prosthesis. This internal configuration in the Kulzer database for that
prepared crown is utilized to design the overlays (reduction trays) for use
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in the preparation of the patient's tooth. In the design of the overlays,
fundamental principles and objectives known in the art are utilized, for
example to remove the minimum amount of original tooth surface.
For example, in a set of overlays or reduction trays, there
may be one overlay or tray for reduction of the medial and distel surface
(front and back) and another tray for the occlusive (top) surface. Also,
there could be two finishing trays which cut lingual (tongue) surface and
buccal (cheek) surface of the tooth. For preparation for a crown, one
would need additional trays for gingival margins.
The foregoing describes a typical use of the method but a
greater or fewer number of reduction trays or overlays may be
appropriate to carry out the preparation of the tooth for later installation
of the dental prosthesis or restoration part.After acquiring the three-
dimensional data of the tooth, this data gets processed by a computer so
as to determine an overlay 1 fitting the teeth 2 of the patient. To this end,
the inner shape of the overlay preferably corresponds to the outer shape
of the tooth to be prepared and to the outer shape of at least part of a
neighbouring tooth. Overlay should fit the teeth in such a manner that
once the overlay is placed onto the teeth, it will only come off by applying
a sufficiently high force to the overlay. During preparation of the tooth,
small forces may be applied to the overlay, which preferably should not
modify the position of the overlay on the teeth. Preferably, the overlay 1
extends over the teeth 2 so as to also cover part of the gingiva 3 or of
neighboring teeth for stability purpose and protection purpose. As the
dentist will use the overlay 1 for removing tooth material, it is
advantageous that the overlay 1 is located onto the tooth in a stable way.
As an example, an overlay 1 closely fitting the tooth, two neighbouring
teeth, and part of the gingiva 3, ensures that a dentist can arrange and
maintain the overlay in a stable position during removal of tooth
structure. When the overlay 1 covers a part of the gingiva 3, at least this
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part of the gingiva 3 will be protected during the process of removing
tooth structure.
It is to be noted that an overlay 1 according to the invention
can cover multiple teeth at once and can be provided to be used by a
dentist in preparing a plurality of teeth using one single overlay 1. This
can be advantageous in the process of preparing teeth for placing
veneers. Such an overlay comprises guiding means, as will be explained
further, for each tooth that needs to be prepared.
The determined overlay 1 has a thickness 4 that mainly
to depends on the required strength thereof, and thus also the material it
will be made of. An overlay 1 according to the invention can have a
constant overall thickness 4. A substantially constant overall thickness is
preferred for an overlay to be used by a dentist in preparing a tooth or
teeth for placing veneers. An overlay to be used for preparing a tooth for
placing a bridge or a crown preferably comprises an upper, guiding part
5, and a lower, supporting part 6. The supporting part 6 of the overlay 1
will ensure that the overlay 1 can be arranged in a stable way onto the
teeth 2, whereas the guiding part 5 of the overlay 1 will guide the dentist
cutting tool and preferably will also determine the maximal penetration
dept of the cutting tool in the tooth. To this end, the thickness of the
guiding part 5 of the overlay 1 will preferably be determined case by
case together with the determination of the guiding means 7, as will be
explained further. The thickness 4 of the supporting part 6 of the overlay
1 can be more freely chosen depending on the preferences of the dentist
and/or the programmation of the computer.
After acquiring the three-dimensional data, this data gets
also processed by a computer so as to determine a predetermined part
of tooth structure to be removed from the tooth by the dentist. The
predetermined part will be determined in view of the further treatment. If
a particular shape of the prepared tooth is required for allowing further
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treatment, the predetermined part will be chosen so that after preparation
of the tooth, this particular shape will remain.
Determining the predetermined part depends on many
parameters and will differ from case to case. Parameters are the location
of the tooth in the mouth of the patient, amount and location of the
damaged tooth structure, distance of the tooth to neighbouring teeth, etc.
In a preferred embodiment, the computer will also take into account the
different parts of the tooth such as the enamel, dentin, pulp, cementum,
etc. in determining the predetermined part. It is also understood within
io the general aspects of the invention that the patient's tooth may have to
be built up through conventional techniques and materials prior to the
actual step of preparation of the tooth, utilizing the overlay.
According to the invention, the computer is programmed to
determine the predetermined part of tooth structure to be removed
without assistance of a dentist except for what concerns the input of the
initial data of the tooth. However also according to the invention, the
computer can be programmed to determine the predetermined part in
cooperation with a dentist, where, for example, the dentist decides on
some parameters. This cooperation can be established by visualizing
data relating to the tooth onto a computer display and allowing the
dentist at least to enter one parameter relating to the preparation of the
tooth. Preferably a preview of the tooth is visualized onto the computer
display together with a preview of a simulation of the prepared tooth, so
as to allow a dentist to see the impact of chosen parameters onto the
prepared tooth. The latter feature provides a larger degree of freedom to
the dentist and allows a less experienced dentist to consult a more
experienced dentist about a case, based on the data in the computer. In
this manner, the method for producing a dentist tool according to the
invention allows a less experienced dentist to decide on a further
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treatment and prepare a tooth for further treatment with a same quality
as if he or she was an experienced dentist.
In another embodiment, the computer is programmed to
determine the predetermined part of tooth structure to be removed in
several phases. At the end of each phase, the computer proposes a
simulated solution to the dentist and requests for approval or correction
of the proposed solution.
Preferably the predetermined part will be determined in
several steps. In a first step, the outer shape of the tooth restoring part is
to be determined so that the tooth restoring part fits with the remaining
teeth and fits into the dental arch of the patient. A bite lift or other
corrective amendment can be directly integrated into the design of the
outer shape. Then, based on this determined outer shape, an inner
shape gets determined that is compatible with the outer shape. In such a
manner, a tooth restoration part can be determined having an optimal
outer shape, and an optimal construction in the sense that it is strong
enough and a minimum of material is needed. In a following step, the
shape of remaining tooth structure is to be determined so that the inner
shape of the tooth restoring part fits the remaining tooth structure after
removal of tooth structure. In a final step, the predetermined part of tooth
structure is determined as the part of tooth structure to be removed to
have the shape of remaining tooth structure left. This way of working
allows determining the outer shape of the tooth restoring part using best
fit programs. Conventionally, the dentist will not follow the steps in the
succession as mentioned above. The dentist will work the other way
around, as the dentist will need to know the shape of the prepared tooth
to determine the inner shape of the restoration part, after which the
dentist will determine an appropriate outer shape. Firstly determining the
tooth restoration part, according to a preferred embodiment of the
invention, results in that a minimum of tooth structure is to be removed
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from the tooth and a maximum conservation of the original tooth structure
can be obtained.
Once the predetermined part has been determined, guiding
means can be determined. The purpose of the guiding means is to guide
a dentist cutting tool, i.e. a drill, along a simulated movement whereby
the cutting tool removes at least a part of the predetermined part. To this
end, it will be understood that in some cases, the dimensions of the
dentist cutting tool, such as the length, diameter, cross-sectional form,
etc. will be determining for which movement is to be made with the
io cutting tool to remove a certain part of tooth structure. It will also be
understood that in many cases, it will not be sufficient to make one single
movement for removing all the predetermined part. Via computer
calculation and/or simulation, one or more movements can be simulated
for removing the predetermined part of tooth structure. It is to be
understood that a movement in this context does not only relates to a
two-dimensional position, but relates to the movement of the cutting tool
in all its aspects such as horizontal movement, vertical movement and tilt
movement.
The guiding means according to the invention comprise at
least two guiding edges 11, 12 (figure 3-6). Two of these guiding edges
11, 12 are spaced apart from each other with a distance d of at least 0,5
mm. The guiding edges 11, 12 are provided to simultaneously contact
the cutting tool 10 thereby guiding the cutting tool 10 at least partially
into a predetermined movement. It is to be understood in this context that
a surface having a length and having a width which are at least 0,5 mm
can be considered as the said at least two guiding edges 11, 12.
Namely, the two outer edges of the surface are provided to
simultaneously contact the cutting tool 10, and are spaced apart with a
distance d of at least 0,5 mm.
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The guiding edges 11, 12 are determined in
correspondence with the simulated movement of the dentist cutting tool
such that both guiding edges 11 and 12 are simultaneously in contact
with the cutting tool following the movement. Preferably, the guiding
edges are simultaneously and constantly in contact with the cutting tool,
preferably during the whole of the movement. The contact between a
guiding edge and the cutting tool, along the movement, is preferably a
point of contact.
Preferably the two guiding edges 11, 12 are spaced apart
io from each other with a distance d of at least 1 mm, more preferably of at
least 2 mm and most preferably of at least 3 mm. Increasing the distance
d between the two edges 11, 12 will increase the guiding quality as it will
be much easier for a dentist to control the cutting tool 10 onto larger
guiding means.
The guiding edges 11, 12 are provided in such a manner as
to be simultaneously contacted by the cutting tool at two contacting
points. As illustrated in figure 3, preferably these contacting points 11,
12, considered on the cutting tool 10, are longitudinally spaced apart by
the distance d. When the cutting tool 10 is arranged substantially
perpendicular to the guiding edges, the distance between the contacting
points will be substantially the same as the distance d between the
guiding edges. Figure 3 illustrates a cutting tool 10 lying simultaneously
against the two guiding edges 11, 12. The guiding edges 11, 12 in this
configuration define a surface along which the cutting tool 10 can be
guided.
However the guiding edges 11, 12 can also simultaneously
contact the cutting tool 10 at two contacting points being located each at
one side of the cutting tool 10, as illustrated in figure 4. In this
configuration, the guiding edges 11, 12 define a guiding groove in which
the cutting tool 10 can be guided. The guiding groove 7 is preferably
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determined so as to define a path laying in the upper surface of the
overlay 1. The groove 7 is provided for guiding a dentist cutting tool
along this path, and to this end, the groove 7 extends through the
overlay so as to form a communication between the inside of the overlay
and the outer environment. When more than one path is to be followed
for removing the predetermined part, multiple guiding grooves 7 will have
to be determined.
A combination of these two mentioned configurations is
illustrated in figure 5. In this figure, a first and second guiding edge 11,
12, being the two guiding edges that are spaced apart, can be seen on
the left hand side, which edges define a guiding surface. A third guiding
edge 13 can be seen on the right hand side, which edge defines,
together with the first and second guiding edge 11, 12, a path. This
configuration therefore allows a cutting tool to be guided into both a
horizontal movement and a tilt.
As can be seen in figure 5, the cutting tool 10 preferably
comprises a collar 14 mounted onto the cutting tool 10. Preferably at
least one of the guiding edges 11, 12, 13 is provided to guide the collar
14 of the cutting tool 10 thereby guiding the cutting tool 10 into a
predetermined vertical position or height or depth. As can be seen in the
figure 5, the guiding groove 7 defining a horizontal path, furthermore
defines a predetermined height 8 for each horizontal location of the
cutting tool, so as to guide the cutting tool 10 along a horizontal path and
in a predetermined tilt, and also guiding the cutting tool in the vertical
way.
Figure 6 illustrates a variant on the embodiment shown in
figure 3, and shows the guiding edges 11, 12, which are provided to
simultaneously contact the cutting tool at two contacting points being
longitudinally distanced from each other. In this embodiment, tooth
structure can be removed that is located in between the two guiding
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edges 11, 12. In particular in preparing a tooth for placing veneers, this
embodiment will be used.
For mounting a crown or a bridge, the tooth is to be shaped
into a truncated pyramid having rounded edges. To this end the outer
and upper part of the tooth are to be removed. This removal of tooth
structure can be guided by the dentist tool according to the invention.
Preferably the removal of tooth structure for preparing a
tooth for mounting a crown or a bridge is performed in several stages
shown in figure 7. In a first stage, shown in figure 7a and figure 8, the
upper part of the tooth gets smoothened. This can be done using an
overlay having guiding edges 11, 12 as illustrated in figure 6. However in
practice, it is preferred that the upper part gets shaped into a V-form. To
this end, the upper part preferably gets smoothened using two guiding
means as illustrated in figure 3, which guiding means are located on both
sides of the tooth in such a manner that said guiding means are provided
guide said cutting tool to cut said upper part into a V-shape.
In a second and a third stage, shown in figures 7b and 7c,
the longitudinal and transversal sides of the tooth get cut, so as to obtain
a truncated pyramid form. The cutting of these sides can be guided by
overlays having guiding means as illustrated in figure 3, 4 or preferably
figure 5. Preferably one overlay comprises two such guiding means each
defining a path extending in the surface of the overlay, the paths
extending parallel to each other, each on one side of the tooth.
In a fourth and fifth stage, shown in figures 7d and 7e, the
edges of the pyramid get rounded. Rounding these edges can be guided
by an overlay as shown in figure 1 and 2. Such an overlay comprises a
path extending in the surface of the overlay and defining a segment of a
circle. Each side of the path is defined by a guiding surface having at
least two guiding edges, as illustrated in figure 3. The height of the
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guiding part 5 of the overlay 1 is defined so as to guide the cutting tool
in a predetermined vertical position.
In this succession of stages, the first stage could be
executed as the last stage instead of as the first. However tests have
5 shown that starting with smoothening the upper part of the tooth is
advantageous in the process of preparing the tooth.
Once the overlay 1 and the guiding means are determined,
the determined overlay 1 having the determined guiding means can be
produced. This can be done by any known means such as a CAD/CAM
10 system, rapid prototyping or 3D printing. When multiple guiding means
have been determined, multiple overlays 1 can be produced each
comprising one or several guiding means. Preferably, a rapid prototyping
apparatus creates the overlay with a tolerance of about 30 pm.
The overlay 1 has, as already mentioned above, a lower,
supporting part 6 and an upper, guiding part 5. As can be seen in the
figures, the guiding part 5 has a certain thickness 8, which defines the
height 8 of the path and enables the cutting tool to be guided in the
vertical way. Preferably the supporting part 6 and/or guiding part 5
comprises a vertical opening 9 from the side to the guiding groove 7,
provided to serve as an entrance into the guiding groove 7 for a dental
cutting tool. In particular when a cutting tool has a tip portion that has a
diameter that is larger than the diameter of the main portion of the cutting
tool, for example a high-speed drill with a tip in the form of a ball, this
opening is advantageous. Entering such a cutting tool into the guiding
groove 7 via the upper part of the overlay would at least partially widen
the guiding groove 7 thereby at least partially taking away its possibility
to firmly guide the cutting tool along the predetermined path.
Furthermore a side entrance 9 is preferred over an entrance via the
upper part as it will be easier to enter the cutting tool in a controlled
manner into the guiding groove 7.
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When a guiding groove 7 is determined to form a circular
path in the horizontal plane, it will be preferred to split up this path into
several segments, and produce multiple overlays 1 each having a
guiding groove 7 corresponding to one segment of this path. This will
result in a set of overlays 1 which can be used by a dentist one after the
other to remove tooth structure following this circular path. Each overlay
1 of the set of overlays 1 will guide the cutting tool along a particular side
of the tooth.
In the embodiment where the predetermined part is not
determined based on the shape of the tooth restoration part, the latter
can be determined based on the data in the computer. Outer shape of
the tooth restoration part can be determined in several ways, all known
to the person skilled in the art. A bite lift or other corrective amendment
can be directly integrated into the design of the outer shape. A first
possibility is to shape the tooth restoration part so that it resembles the
outer shape of the original tooth. A second possibility is to shape the
tooth restoration part so that it fits with neighbouring teeth. A third
possibility is a combination of the first and second, and modifies the
shape of the original tooth to better fit with the neighbouring teeth. Inner
shape of the tooth restoration part will be determined based on the
simulation of the preparation of the tooth. As the tooth will be prepared in
a guided manner, it is known in advance what the shape will be of the
prepared tooth. The inner shape of the tooth restoration part will be
chosen so that it fits the shape of the prepared tooth.
Preferably the method according to the invention further
comprises the step of producing a tooth restoration part.
Similar to the determination of the predetermined part, a
tooth restoration part can be determined by a computer without any
interaction of a dentist. However it will be preferred that the computer
determines the tooth restoration part in cooperation with a dentist, for
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example in a way as described above. The computer can, in this process
of determining a tooth restoration part, perform predetermined clinical
checks and alert the dentist in case the tooth restoration part does not
meet the standard norms. This will enable a dentist to design a tooth
restoration part in a fast and reliable manner.
The production of the tooth restoration part can be done by
any means known to the skilled person such as a CAD/CAM system.
